Medical Applications of Nuclear Sciences Ilham Al Qarada… · –Nuclear Medicine for diagnostic...

Medical

Applications of

Nuclear Sciences

Ilham Al-Qaradawi Professor of Physics, Qatar University

Doha, Qatar

WNU-SI 2012 Oxford - UK

Outline

• Areas of nuclear medical uses

• Medical imaging

• X-ray and CT

• Magnetic Resonance Imaging (MRI)

• SPECT

• PET and PET/CT

• Accelerators applied to medicine

• Treatment therapies

• Summary


Medical applications

• Diagnostic; Medical imaging (Radiology): creating images

of internal human body or its functions

– X-rays and CT

– Magnetic Resonance Imaging (MRI)

– PET and PET/CT, PEM

• Treatment;

– Conventional radiation therapy

– Brachytherapy

– Hadron therapy

– Antiproton therapy

• Irradiation and sterilization.


Anatomical Imaging

• X-ray (Radiography and Fluoroscopy)

• Computerized Tomography, CT

• Magnetic Resonance Imaging, MRI


X-ray Radiography

• Radiography involves the use of an X-ray tube and a photographic plate.

• The patient is placed between the two and an image is produced on the film of the area exposed.

• A common “chest X-ray” is an example of a radiographic X-ray.


Fluoroscopic x-ray imaging

• In a fluoroscopic X-ray machine the film is substituted with an imaging device (image intensifier) which enables the radiologist to observe the part of the body exposed live on a video monitor.

• A blocking agent, such as barium, is often swallowed by the patient to allow the medical staff to observe internal processes in action.

• A fluoroscopic examination can be used to locate ulcers.


X-ray image versus CT scan

• A conventional X-ray image gives a shadow of the body

• organs and tissues of different densities show up differently on the radiographic film.

• Depending on where the lamp is, you see the outline of the pineapple or the banana.

C - RECONSTRUCTION

A – LINEAR SAMPLING

X RAYS

TUBE

DETECTOR

CO

UN

TS

B – ANGULAR SAMPLING

X RAYS

COMPUTERIZED TOMOGRAPHY

This is the basic idea of computer aided tomography. In a CAT scan machine, the X-ray beam moves all around the patient, scanning from hundreds of different angles. The computer takes all this information and puts together a 3-D image of the body.

X-ray computerized tomography (CT)

MAGNETIC FIELD: 1.5 – 3 Tesla

1H

SPIN

RF

PULS

E

RELAXATION

MRI

SIGNA

L

EXCITATION

M M M

B0

B0

B0

H2O

Magnetic Resonance Imaging (MRI)

Magnetic field applied


MRI of upper torso (courtesy NASA)

MRI of knee

MRI of shoulder

Magnetic Resonance Imaging: morphology


Functional Imaging

• Reveal structure

through function

• Image produced

depends on biological

distribution of

compound in vivo


Scintigraphy by Gamma Camera

• Used to record emitted internal radiation from

injected isotopes to create two dimensional images.


SPECT (Single photon emission computed tomography)

• Uses gamma cameras, of multi-

heads slowly rotated around the

patient.

• Able to provide true 3D

information.

• Information presented as cross-

sectional slices.

• 85% of all nuclear medicine

examinations use Mo/Tc

Generators for diagnostics of

liver, lungs, bones.


Medical radionuclides

• Radionuclides are used in medicine

by two general classifications:

– Nuclear Medicine for diagnostic

procedures

– Radiation Oncology for radiation

therapy.

• Nuclides used for

radiopharmaceuticals:

– should decay by emitting only photons

– Should have a short effective half-life.

– Technetium-99m and Indium-113m are

commonly used radiopharmaceuticals.


Nuclear Medicine

• Radionuclides are used to determine the extent of a medical problem in a patient.

• The radionuclide is “attached” to a pharmaceutical, which has the properties to deposit the radioisotope in the organ of concern for a patient.

• External radiation detectors are used to determine abnormalities in the organ.

• Thyroid scan and lung function tests are examples.


Tracer techniques

• Different parts of the human body absorb different elements but do not discriminate between different isotopes.

• In tracer techniques a radioactive isotope, such as iodine, is injected.

• The signals coming from the resulting radiation then give an image of the area where the isotope was absorbed.

• Usually isotopes of a relatively short half-life, of the order of minutes or days, are used to minimize long-term radiation damage.

Photo taken from Alan

Walter presentation


Radiochemistry

• Medical isotopes

separated under sterile

conditions

• Radiation dose to

operator must be

minimized

• Must be completed

quickly (less than one

half-life)


Sources of radioisotopes

Cyclotron Research Reactor

Use charged particles Use neutral particles

Produce short lived isotopes Produce longer lived isotopes

neutron deficient nuclei neutron rich nuclei

Cyclotrons vs. Reactors


Mo-99 from reactors

• Mo-99 is the most “in demand” medical isotope

• Mo-99 is shipped around (66 hrs half life)

• Its “decay product” Technetium-99m is used as

tracer

• Comes “easily” from a handful of existing,

publicly funded nuclear research reactors

• Reactors are getting old


Crisis of 99Mo

• 30 million examinations/year rely on 99Tc

• Worldwide production of 100 kilo curies per

year produced at aging nuclear reactors – BR2 Belgium

– National Research Universal (NRU) Reactor Canada

(50%)

– OSIRIS France

– HFR Netherlands (40%)

– SAFARI-1 South Africa

• Canadian NRU was off for repairs middle of

2009 to August 2010, Netherlands down for

repairs

• Almost 90% of world Mo supplied by the 2

closed reactors


Effect of 99Mo Crisis

• The price of Molybdenum-99 rose considerably

during the crisis, causing some anxiety among

buyers.

• The two major reactors are now back in operation.

• IAEA helps to close radioisotope production gap.

• Canadian Light Source (CLS) started a project to

explore the technical and economic feasibility of

using electron linear accelerator to produce Mo-99,

the “parent isotope” of Tc-99m.


Positron Emission Tomography (PET)

• PET (positron emission tomography)

scans involve the injection into the

body of an isotope which decays by

positron emission.

• When this positron encounters an

electron they annihilate each other,

emitting two photons.

• The energy and path of these photons

leaving the body can then be used to

give an accurate picture of the area

where the isotope was absorbed.

http://en.wikipedia.org/wiki/File:ECAT-Exact-HR--PET-Scanner.jpg

Positron Emission Tomography (PET)

J. Long, “The Science Creative Quarterly”,scq.ubc.ca

Cyclotron

Radiochemistry


PET

• When a pair of detectors detects

simultaneously one 511keV photon

each, a positron must have annihilated

on a straight line connecting those two

detectors – the so called line of response.

• The multitude of all these lines of

response is used to calculate a slice

image in a certain plane.

• produces a three-dimensional image or

picture of functional processes in the

body


PET Applications

• Oncology:

– Thyroid

– Sarcoma

– Lung

– Melanoma

– Lymphoma

– Head & neck

– Breast

• Neurological Applications:

– Parkinson’s, Alzheimer’s, Addiction

[11C] FE-CIT

Normal Subject

Parkinson’s disease

Courtesy HSR MILANO

PET functional receptor imaging


PET Isotopes

Nuclide Half-life Tracer Application

O-15 2 mins Water Cerebral blood flow

C-11 20 mins Methionine Tumour protein synthesis

N-13 10 mins Ammonia Myocardial blood flow

F-18 110 mins FDG Glucose metabolism

Ga-68 68 min DOTANOC Neuroendocrine imaging

Rb-82 72 secs Rb-82 Myocardial perfusion


• Most widely used PET tracer

• Glucose utilization allows assessment of glucose

metabolism in the heart, lungs, and the brain

• Taken up readily by most tumours

• Must be completed quickly (less

than one half-life)

FDG (Fludeoxyglucose 18F)

Mammography PET (PEM)

• Clear Crystal Collaboration (CCC) at CERN working on a dedicated PET for mammography; the Clear PEM.

• The aim is to be able to detect small tumours with a diameter of 1mm to 2mm in the breast and axilla region.

• Many advantages of PEM over x-ray mammography and whole body PETs

• PEM currently employed in hospitals (such as CHU Hopital Nord Marseille, France).

• Since tumour specific pharmaceuticals are used, the probability of false diagnosis due to the presence of inflammation, is reduced considerably.


PET/CT

• Combines the functional information with the

anatomical detail

• Images from both devices are superimposed (co

registered).

• Higher diagnostic accuracy than PET or CT

alone

• An emerging imaging

technology, not yet available is

PET/MRI.


Accelerators for all stages

• Isotope production

• Treatment therapy

Types of Accelerators

• Cyclotrons

• Syncrotrons

• Linacs


Low-energy cyclotrons for production of radionuclides for medical diagnostics

Medium-energy cyclotrons and synchrotrons for hadron therapy with protons (250 MeV) or light ion beams (400 MeV/u 12C-ions)

Electron Linacs for conventional radiation therapy, including advanced modalities:

•Cyberknife •IntraOperative RT (IORT) •Intensity Modulated RT

Three classes of medical accelerators


Cyclotrons used in medicine

• Baby Cyclotrons (< 18 MeV) in-house facility

• Mainly used for production of short-lived positron emitters

like 18F, 11C, 13N, 15O.

• Medium Energy Cyclotrons (< 40 MeV), centralised

facility

• Majority of the cyclotron produced isotopes are produced

using such machine viz, 123I, 201Tl, 67Ga, 68Ga, 103Pd etc.

• High Energy Cyclotrons (above 40 MeV), centralised

facilities and research institutions: Used for production of

few radioisotopes requiring high energy for production viz, 67Cu, 82Sr, 211At…


Baby Cyclotrons

• Accelerated protons


Medium energy cyclotrons


High-energy cyclotrons

• IBA‟s ARRONAX in

Nantes

• 4 Particles: H- / D- / He2+/

HH+

• Variable energy: 15 MeV-

70 MeV


Varian Clinac 1800 installed in the S. Anna Hospital in Como (Italy)

Medical accelerators: electron linac


Radiation and electron therapy

• Radiation is used to destroy

tumors present in an organ.

• Electrons or Cobalt-60 sealed

source are generally used for the

high activity.

• A mechanical device moves the

source to an opening in a

collimator which projects a beam

of photons used for treatment.

CyberKnife system is a method of delivering radiotherapy, with the intention of targeting treatment more accurately than standard radiotherapy.

http://www.accuray.com/Products/Cyberknife/index.aspx

6 MV Linac mounted on a robotic arm

CyberKnife (CK) Robotic Surgery System

It is a highly precise, image guided radiation

therapy delivery system capable of taking care

of the motion during treatment.



Brachytherapy

• Brachytherapy represents an effective

treatment option for many types of

cancer. A source is placed inside or next

to the area requiring treatment.

• Tumours can be treated with very high

doses of localised radiation, whilst

reducing the probability of unnecessary

damage to surrounding healthy tissues.

• In some cases radioactive seeds of < 1

mm are injected into the tumour area.

• can be used alone or in combination

with other therapies.


Protons and ions spare healthy

tissues

• Unlike photons or electrons,

proton beams deposit most of their

energy at the end of their paths in

the so-called Bragg peak.

• Hence, targeting deep-seated

tumours, close to sensitive organs,

with much reduced risk to

surrounding healthy tissue.

• benefit of proton and heavy-ion

therapy is that the beams can be

"tuned" to deliver a high dose of

energy at a precise location


Proton Therapy

• As well as an accelerator, a

gantry is required; this is a

massive structure that allows

directing the beam to the

tumour from any direction.

• It carries the final section of

the beam line and the beam

spreading ‘nozzle’


Therapy with carbon ions

• Carbon allows extremely precise targeting of the

tumour.

• lighter particles such as protons, whilst

depositing their energy in the Bragg peak, cause

far fewer double-strand breaks than heavier

ones like carbon.

• Tumours eligible for carbon ion radiotherapy so

far are: skull base tumours and tumours close to

the spinal chord.


Antiproton Cancer Therapy

• Researchers at CERN found that antiproton, can effectively treat

cancer.

• Antiprotons strip electrons off atoms in cells, causing ionization

and killing the cell they are in.

• A proton beam could also be used for ionization but when

antiproton beam eventually come to a stop at the focus, the

annihilation of both particles will release a huge amount of energy

(in the context of a single cell)....which is much more effective at

killing selected cells than simple ionization.

• Scientists estimate that routine clinical application of matter-

antimatter annihilation to cancer treatment should be a reality in

10-15 years.


Sterilization

• Medical equipment and Blood

• Sterilization by gamma irradiators or accelerators.


Conclusions

• Radiotherapy is a proof that the damaging effect of

radiation has itself been of great use.

• New isotope production and separation techniques are

needed to provide a steady supply of medical isotopes.

• Accelerators may solve the technetium crisis.

• Automation, robotics, and technology are necessary

aspects.

• Molecular imaging is enhancing health care by

providing early detection and better treatment of

tumors with less side effects on healthy tissue.


Takeaway points

• The progress in the field of radiation applications is not only

driven by advancement of nuclear and radiation physics but also

by the development of technology.

• Better planning, research and cooperation worldwide are

required to avoid future radioisotope production crisis such as

Mo-99.

• What seemed to be pure or basic science research in the past have

had large impact on applications of medical imaging such as ion

beam therapy.

• Research is required to find techniques to reduce the damaging

effects on healthy cells and target diseased cells more effectively.


Issues for consideration

• Cyclotrons versus research reactors for isotope

production.

• Cyclotrons versus synchrotrons for hadron

therapy.

• Dose accuracy and dosimetry: Radiation

protection for workers and patients

• Cost of nuclear medicine!


Thank you for your attention

[email protected]

Questions?

mailto:[email protected]

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